254 WORK OF THE NATIONAL GEOGRAPHIC SOCIETY 
Still Later it was observed that rivers are diverted, lakes filled 
up, and islands submerged through natural agencies ; it was also 
found that many shore lines are shifting, that some lands are 
rising and others sinking, that all continents are wasting through 
the action of rain and rivers, and that the waste of the land is 
carried into the seas ; thus geology grew up, and a time element 
was introduced even into that part of geogra})hy which deals with 
the more persistent earth-forms. In this stage geographic features 
were assumed to he changeable, and they were described not only 
in terms of form and position, hut in terms of stage or sequence. 
This ma}' he called transitional or medieval geography, though 
it comes down to the present in the books, and many geographers 
and some geographic societies have not yet risen above its plane. 
Modern students of earth-forms have observed that rivers cut 
their own valleys in definite wa}^s and at definite rates depend- 
ing on known conditions, and that eventually the running waters 
carve the land into hill and dale, mountain and plain, in a defi- 
nite way, albeit varying with altitude, structure, and other con- 
ditions. With recognition of the agencies and conditions of 
geographic change geogra[)hic history became definite, and it was 
found ])ossilde to interpret the record of ages of continent-growth 
from the geographic features, great and small, displayed by the 
continent. In this way a new science was developed; some- 
times it is called the new geograph3^ sometimes the new geology, 
sometimes geomorphologj" or geomor})hy. It matters little what 
the science is called, but it is important to remember that through 
recognition of causes and conditions geography was raised to the 
plane of science. This is modern geogra])h\"; and in this stage 
geographic features are regarded as definite products of known 
agency , and thus as definite records ot’determinate history, and de- 
scription in terms of form and position is but a means to a nobler 
end, the reading of world-history from geographic features. 
So three epochs in geographic development may be recognized, 
and their importance is none the less because some of their fac- 
tors overlap— for the overlapping of factors is one of the charac- 
teristics of development. The first was the ancient or empiric 
e{)Och ; the second was the transitional or scholastic epoch ; the 
third is the modern or scientific epoch. In its first epoch geog- 
raphj' was a meager bod}" of description of features and a crude 
art of describing ; in the second epoch it became a richer body of 
description of stages as well as features, and the art of describing 
was improved ; and in so far as it has entered into the third 
